Epsilon Open Archive

Abstract

The objective of this thesis was to investigate the influence of habitat and landscape factors on butterfly diversity and movement in grasslands. The studies were carried out in two agricultural areas in Southern Sweden that differed in landscape structure, including habitat amount and field size. The results show that both habitat characteristics and landscape structure influenced species numbers and abundance of butterflies in grasslands. The amount of adjacent forest, flower abundance, field size and estimated nutrient levels were factors identified as influencing butterfly species composition. Mark-release-recapture experiments with two grassland butterflies (meadow brown, Maniola jurtina L. and scarce copper, Lycaena virgaureae L.) indicated that these species regularly move over distances of several hundred metres in a landscape with a high amount of habitat. The differences in movement pattern between the two species were greater in terms of movement frequency than total distances. A comparison with results of published mark-release-recapture data for the two studied species and other butterflies, made evident the dominant impact of the size of the study area on mean movement distances. A comparison of the movement patterns of the same species (Maniola jurtina) in the two different study areas showed that dispersal differed between the two areas. Dispersal rates were much lower in the study area with a low amount of habitat. The factors influencing patch immigration differed between the two study areas. The dispersal functions fitting proportions of individuals that moved were also different, which can be important in the context of modelling movement. In marginal agricultural areas, abandonment is the greatest threat to semi-natural grasslands. Different degrees and patterns of abandonment were estimated to affect butterfly diversity and movement quite differently. This emphasises the importance of spatial planning for landscape change in agricultural areas in order to minimize negative impacts on species diversity.